On 10/21/2016 02:58 PM, Michael Matz wrote:
+This function returns the same value as \code{\_Unwind\_GetIP}. In
+addition, the argument \code{ip\_before\_insn} must not be not null, and
+\code{*ip\_before\_insn} is updated with a flag which indicates whether
+the returned pointer is at or after the first not yet fully executed
+instruction.
I think this is rather misleading. On x86_64, the location of the IP value is the same for calls and asynchronous signals: it always points to the next instruction to be executed. There are no partially executed instructions.
The difference that if we unwind through a call which has not yet returned, the caller is assumed to be still within the exception handling region in which the call instruction is located. This is the consequence of the desired exception handling semantics of a non-returned function call. It is not directly related to the instruction pointer value returned by _Unwind_GetIPInfo.
This is different for the signal case. There, the instruction pointer directly determines the active exception handling region.
Florian